1. Field of the Invention
The present invention relates to a photosensitive polymer composition, to a method of using the composition for forming relief patterns, and to electronic parts. More precisely, it relates to a positive-type, heat-resistant photosensitive polymer composition capable of being into a heat-resistant polyimide polymer under heat, which is suitable for surface-protecting films, interlayer insulating films and others for electronic parts such as semiconductor devices, etc., to a method of using the composition for forming relief patterns, and to electronic parts.
2. Description of the Related Art
Polyimides have good heat resistance and good mechanical properties, and are readily formed into films of which the surface could be well planarized. Having those advantages, they are widely used for surface-protecting films, interlayer insulating films and others for semiconductor devices.
Where polyimides are used for surface-protecting films or interlayer insulating films, the step of forming through-holes and the like in those films is achieved essentially in an etching process in which is used a positive-type photo-resist. However, the step comprises applying and removing such a photo-resist, by which the step is complicated. This is the problem with the step. For the purpose of rationalizing the working step, heat-resistant materials with photosensitivity have heretofore been studied.
Relative to photosensitive polyimide compositions, for example, known are (1) a polyimide precursor composition in which is introduced a photosensitive group through ester bonding (JP-B-52-30207, etc.), and (2) a composition as prepared by adding a compound that contains a carbon-carbon double bond capable of being dimerized or polymerized by the action of chemical rays, an amino group and an aromatic bisazide, to a polyamidic acid (JP-B-3-36861, etc.).
In use of such photosensitive polyimide compositions, in general, a solution of the composition is applied onto a substrate, then dried, and exposed to active rays via a mask, and thereafter the non-exposed area is removed with a developer to form a pattern on the substrate.
However, the compositions (1) and (2) noted above are both negative-type ones, and the development for these requires an organic solvent. Therefore, when an etching process of using a positive-type photo-resist is switched to the process of using the negative-type photosensitive polyimide, the problem is that the mask for the exposure device and the development equipment must be changed.
On the other hand, relative to positive-type photosensitive polyimides, for example, known are (3) a polyimide precursor in which is introduced an o-nitrobenzyl group through ester bonding (JP-A-60-37550), and (4) a composition comprising a phenolic hydroxyl group-having polyamidate and an o-quinonediazide compound (JP-A-4-204945).
However, the precursor (3) is essentially sensitive to light having a wavelength of not longer than 300 nm, and its sensitivity is low. Therefore, the precursor (3) is problematic in that an i-line stepper (for single wavelength light of 365 nm) which is much used these days in the art is hardly applicable thereto. On the other hand, the composition (4) is also problematic in that its sensitivity is still unsatisfactory even though higher than the sensitivity of the precursor (3). At present, no one could obtain positive-type photosensitive polyimides having satisfactorily good sensitivity.
The present invention is to overcome the problems noted above in the related art.
Specifically, the invention provides a positive-type, heat-resistant photosensitive polymer composition, which has high sensitivity and does not take much time for development.
The invention further provides a positive-type. heat-resistant photosensitive polymer composition, which has higher sensitivity or higher resolution, requires shortened development time, or give better patterns.
The invention also provides a method of using the high-sensitivity composition for forming good relief patterns with high resolution.
The invention still provides high-reliability electronic parts having such good relief patterns.
The photosensitive polymer composition of the invention comprises (a) a polyimide precursor or a polyimide which is soluble in an aqueous alkaline solution, (b) a compound capable of generating an acid when exposed to light, and (c) a compound having a phenolic hydroxyl group.
The composition may additionally contain (d) a dissolution retardant for the component (a) in an aqueous alkaline solution.
In the composition, preferably, the component (b) is an o-quinonediazide compound.
Also preferably, the component (a) in the composition is a polyamidate or a polyimide.
Still preferably, the component (a) is a polyamidate having repetitive units of a general formula (I): 
wherein R1 represents a tetravalent organic group; R2 represents a divalent organic group having a carboxyl group or a phenolic hydroxyl group; and two R3""s each independently represent a monovalent organic group.
Still preferably, the component (c) in the composition is a compound of a general formula (II): 
wherein X represents a single bond or a divalent group; R4 and R5 each independently represent an alkyl group; and m and n each independently represent an integer of from 0 to 3.
Still preferably, X in the compound of formula (II) is selected from the following groups: 
Still preferably, the compound of formula (II) is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.
Still preferably, the component (c) is a compound of a general formula (III): 
wherein Y represents a single bond or a divalent group; R6 and R7 each independently represent an alkyl group; and p and q each independently represent an integer of from 0 to 3.
Still preferably, Y in the compound of formula (III) is a divalent organic group having one or more aromatic rings.
Still preferably, the component (c) is a compound having a methylol group and a phenolic hydroxyl group.
Still preferably, the compound having a methylol group and a phenolic hydroxyl group is represented by a general formula (IV): 
wherein Z represents a single bond or a divalent group; R8 and R9 each independently represent an alkyl group or an alkenyl group; r and s each independently represent 1 or 2; and t and u each independently represent an integer of from 0 to 3.
Still preferably, Z in the compound of formula (IV) is a group of: 
wherein two A""s each independently represent a hydrogen atom, or an alkyl group having from 1 to 10 carbon atoms.
Still preferably, the compound of formula (IV) is 3,3xe2x80x2-methylenebis(2-hydroxy-5-methylbenzenemethanol).
Still preferably, the component (d) in the composition is selected from an onium salt, a diaryl compound or a tetraalkylammonium salt.
Still preferably, the component (d) is selected from a diaryliodonium salt, a diaryl sulfone compound, a diarylurea compound or a tetramethylammonium halide compound.
Still preferably, the component (d) is a diaryliodonium salt of a general formula (V): 
wherein R10 and R11 each independently represent a monovalent organic group, and R10""s and R11""s may be the same or different; v and w each independently represent an integer of from 0 to 5; and Xxe2x88x92 represents a counter anion.
Still preferably, the composition contains from 5 to 100 parts by weight of the component (b) and from 1 to 30 parts by weight of the component (c), relative to 100 parts by weight of the component (a).
Still preferably, the composition contains from 0.01 to 15 parts by weight of the component (d) relative to 100 parts by weight of the component (a).
The method of the invention of using the photosensitive polymer composition for forming relief patterns comprises a step of applying the composition onto a substrate and drying it thereon, a step of exposing it, a step of developing it, and a step of heating it.
Preferably, in the method, the light to be used in the exposing step is of i-line.
The electronic part of the invention has the relief pattern as formed in the method noted above, in which the relief pattern acts as a surface-protecting film or an interlayer insulating film.